This is a renewal application for an interdisciplinary project to understand the biological barriers to protein and DNA transport at mucosal surfaces and to produce new polymeric delivery systems to enhance immune protection within the female reproductive tract. In the past periods of support, we demonstrated that: antibodies (Abs), other proteins, and DNA can be slowly released from biocompatible polymer matrices and microspheres; these agents are active at the mucosal surface; human Abs, plasmid DNA, and other macromolecules can diffuse as fast through human cervical mucus as they do through water; a polymer vaginal ring can continuously release active Abs or DNA that becomes well-distributed throughout the vaginal secretions of a mouse for 30 d; vaginal rings releasing anti-herpes Abs can prevent genital infections in mice and vaginal rings releasing antigens can stimulate a long-lasting, mucosal immune response to sperm antigens in the mouse; orally-administered polymer microparticles loaded with Vg can stimulate mucosal immunity in the vagina; surface modification of particles can influence local transport and antigen processing in dendritic cells; DNA delivered at the mucosal surface can transfect local cells, which leads to local immunity; and mucosal delivery systems that deliver DNA vaccines encoding SIV proteins can protect rhesus macaques from mucosal challenges of SIV. We now propose a novel modular approach to the design and synthesis of biodegradable nanoparticles using modular design to add multiple functions. Our experiments are designed to quantify the barriers to nanoparticle transport at these tissue sites, and to develop polymeric drug delivery systems that overcome the barriers. We propose the following interrelated specific aims: 1) Development and characterization of multifunctional nanoparticle delivery systems for peptides, DNA, and siRNA; 2) Design of new and use of existing delivery systems to examine DNA delivery and siRNA delivery in the intestinal, respiratory, and reproductive tracts of the mouse; and 3) Development of new delivery systems to examine approaches for prevention of unwanted pregnancy and treatment of HIV infection.